Chaos in general relativity

Is coordinate invariant. A new study shows that general relativity, a nonlinear theory in which observers in different reference frames measure time differently, is not incompatible with chaos, a theory for nonlinear systems in which events unfold in absolute time. A physical system–-a weather system, say–-is chaotic if a very slight change in initial conditions sends the system off on a very different course. How different? The degree to which a system is chaotic can be encapsulated in a parameter called the Lyapunov exponent: When it is positive, the system is chaotic; when negative or null, the system is nonchaotic. For many years, physicists worried that a shift in a frame of reference might also alter the time parameter in such a way as to change the Lyapunov exponent from null or negative to positive or vice versa. Adilson Motter of the Max Planck Institute for the Physics of Complex...